Patent literature 1 discloses measuring, by a mobile terminal or a network (i.e., a base station or a gateway), duration time of an inactive state during which the mobile terminal does not perform communication, and causing the mobile terminal to transition to a sleep mode when the duration time exceeds a predetermined expiration period. Patent literature 1 further discloses measuring, by a mobile terminal or a network (i.e., a base station or a gateway), a frequency of communication of the mobile terminal, and changing the timer expiration period regarding the sleep mode transition based on the frequency of communication of the mobile terminal. Patent literature 1 further discloses changing the timer expiration period regarding the sleep mode transition based on remaining battery power of the mobile terminal.
Further, Non-patent literature 1 and 2 disclose that subscriber data managed by a Home Subscriber Server (HSS) includes configuration data of a UE inactivity timer in a 3rd Generation Partnership Project (3GPP) mobile communication system. The UE inactivity timer is a timer that measures duration time of an inactive state during which user data regarding a mobile terminal is not transmitted or received. The UE inactivity timer is (re)started by a base station, and is used to determine the change of state of the mobile terminal from a CONNECTED state to an IDLE state. The configuration data of the UE inactivity timer held by the HSS is transmitted to the base station from the HSS through a Mobility Management Entity (MME) in response to attach of the mobile terminal, location registration update, a service request or the like.
The following are definitions of the terms “CONNECTED state” and “IDLE state” used in this specification and Claims. The “IDLE state” means a state in which a mobile terminal does not continuously transmit or receive control signals for session management and mobility management to or from a mobile core network, and radio resources in a radio access network have been released. The radio access network is, for example, UTRAN or E-UTRAN. The mobile core network is, for example, a General Packet Radio Service (GPRS) packet core or an Evolved Packet Core (EPC). One example of the IDLE state is an EPS Connection Management IDLE (ECM-IDLE) state and a Radio Resource Control IDLE (RRC_IDLE) state of the 3GPP. In the RRC_IDLE, radio resources in the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) have been released.
Meanwhile, the “CONNECTED state” means a state in which, as in an ECM-CONNECTED state and an RRC_CONNECTED state of the 3GPP stated above, radio resources at least for transmitting and receiving control signals (control messages) for session management and mobility management between the mobile terminal and the mobile core network are secured in a radio access network, and such a connection is established as to be able to transmit and receive control signals (control messages) between the mobile terminal and the mobile core network. In short, the “CONNECTED state” is a state in which the mobile terminal is connected to the mobile core network so as to be able to at least transmit and receive the control signals (control messages) for the session management and the mobility management. In other words, the “CONNECTED state” does not require a state in which a data bearer is configured for transmitting and receiving user data between the mobile terminal and an external packet data network (PDN). The “CONNECTED state” can also be called an “ACTIVE state”.
Typically, the mobile core network manages the location of a mobile terminal which is in the CONNECTED state on a cell by cell basis, and manages the location of a mobile terminal which is in the IDLE state in units of location registration areas (e.g., tracking areas, routing areas) including a plurality of cells. When moved from one location registration area to another location registration area, the mobile terminal which is in the IDLE state transmits a message indicating an update of the location registration area to the mobile core network. The mobile core network transmits, upon arrival of downlink traffic (downlink data or incoming voice call) to the mobile terminal which is in the IDLE state, a paging signal to a paging area defined based on the location registration area.